Dynamically-Selectable Multi-Modal Modulation in Wireless Multihop Networks

ABSTRACT

In a self-organizing wireless multihop network, each node device selects operation among short-range (SR) and long-range (LR) communication modes, among which the SR mode uses a higher data rate than the LR mode. Each node device advertises connectivity link availability for neighboring node devices, and selectively initiates a link in response to connectivity availability advertised by at least one neighboring node device. The availability advertising is performed in the SR and the LR communication modes, according to a periodicity that is dynamically-variable in response to prevailing circumstances in the local neighborhood. The link initiation is selectively performed in one of either the SR or the LR communication mode based on selection criteria that include data throughput performance associated with different neighboring node devices with which connectivity is available via a certain communication mode.

FIELD OF THE INVENTION

The invention relates generally to data communications via wirelessmultihop networks and, more particularly, to asynchronous multi-modalcommunications in self-organizing and self-adapting networks.

BACKGROUND OF THE INVENTION

A wireless multihop communications network, such as a mesh network,includes a set of node devices capable of exchanging messages with oneanother over a wireless medium, typically using radio frequency (RF)communications. Each of the node devices can be primarily acommunications device or, alternatively, the communicationsfunctionality may be secondary to its primary function. For example, ina given node, the communications circuitry can be a part of a devicesuch as a computer system, a smart appliance, a vehicle, a media device,a piece of industrial equipment (e.g., an instrument, machine, sensor,actuator), and the like.

In a multi-hop mesh architecture the node devices are uniquelyaddressable, and are capable of selecting among sets of alternativeintermediate node devices in establishing a communications path to routemessages from an originating node device toward the intended destinationnode. The particular path from the origination device to the destinationis a function of the criteria defined within the routing protocolapplied within the network. In general, each of the node devices can bean originating and destination node device as well as act as a relaydevice. Thus, node devices perform both, message forwarding, and messageorigination/consumption functions. This also means that communicationlink activity can be variable across the network and quite heavy atcertain devices of the network as a function of the source-destinationtraffic patterns and the available intermediate devices' connectivity.

Wireless multi-hop mesh networks in particular face other challenges.For instance, wireless links may not always be reliable: there may beintermittent interfering signals, intermittent obstructions, includinglarge movable objects (e.g., vehicles) moving in and out of thetransmission path, weather affecting the quality of radio signalpropagation, etc., affecting the signal strength of transmissions seenby the receiving node. Also, certain node devices may be situated nearthe limits of their radio's communication range, relative to a nodeneighbor, which further compounds signal reception challenges.

In ad hoc, multi-hop RF mesh networks nodes form dynamic associationswith their local neighbors. In general, network connectivity isestablished based on node information broadcasts and dedicated routinginformation communications exchanges between neighbor devices. Evaluatedlink connectivity and routing information exchanges allow each node toderive optimal forwarding paths to other nodes in the network and togateway nodes that act as the access points into and out of the RFnetwork.

In a multi-hop network, nodes can receive or initiate neighborconnection requests for network route maintenance or to relay trafficacross the network at any time. However, with a single RF transceiver,each node is limited to communicating with a single neighbor at anygiven time. Where nodes operate in a single communications mode (asdefined, for example, by particular frequency channelization,transmission modulation, or multi-access methods), an idle node is ableto continuously monitor for neighbor connection requests and caninitiate its own connection to a selected neighbor at any time.

Where nodes are capable of operating in more than one transmission mode,such as where nodes can selectively transmit using different modulationtechniques, there needs to be a higher degree of coordination ororganization if nodes are to be able to asynchronously connect withneighbors with minimum delay when a connection needs to be establishedfor routing exchange, message relay, or other communications exchange.One known way to coordinate the multiple modes in a multi-hop meshnetwork relies on some form of centralized timing control in whichnetwork-wide time synchronization prescribes dedicated time periodsduring which the different transmission modes can occur at particularnodes. For ad hoc networks, where there can be dynamic, overlapping setsof associations between groups of nodes that are within radio range ofone another, such a centralized coordination approach would beunfeasibly restrictive. It would be inefficient and impractical topre-define periods for communications in one mode or the other for eachand every node across the network. If such an approach were attemptedfor a generalized communications network, the asynchronous, stochasticnature of initiated network connections and data flows would result insignificant network delays in the transfer of data betweensource-destination points. At each hop traffic would be forced to waitfor the time availability of the particular mode in communicating fromone neighbor to the next along the forwarding path. Furthermore, wherenodes in a multi-hop or mesh network environment can have tens or evenhundreds of neighbors depending on network size, any form of centralizedcontrol would severely constrain the practical limits of networkscalability.

A solution is needed for a practical, adaptive network, in whichmulti-mode communications can be utilized effectively, particularlyunder dynamically changing circumstances and traffic exchanges that maybe associated with a general ad hoc network.

SUMMARY OF THE INVENTION

One aspect of the invention is directed to a distributed, looselycoupled, ad hoc communications network in which node devices can operatein two communication modes: a long-range communication mode, and ashort-range communication mode. The long-range communication mode offersgreater reliability and geographic separation between connectable nodes,whereas the short-range communication mode offers faster (higher speed)data transfer rate. Individual node devices implement localized controland coordinate their own transitions between communications modesaccording to their present circumstances, such as whether they haveestablished node neighbors capable of operating in either one or bothmodes, for example, and with how many such neighbors a given node devicehas established connectivity. In such a system each node device canlocally decide which communication mode should be used to access thenetwork given available neighbor link alternatives. The decision can bebased on such factors as data throughput performance offered throughvarious neighboring nodes, or based on specific connectivityrequirements for a given application service.

In a related aspect of the invention, each node device providesconnectivity to its neighbors in both communication modes, allowingthose neighboring nodes to independently select the communication modewith which to establish connection to the node device. Regardless of themode of connectivity used by any given node device, and whether thatdevice may or may not have neighbors connected in certain communicationmodes, support is maintained for connectability in both modes. Incertain embodiments, the degree of this connectability is varied toefficiently suit the prevailing circumstances in the local neighborhood.

In one example embodiment, a node device is provided for use with aself-organizing wireless multihop network containing a plurality ofother node devices and at least one gateway device, each node devicebeing within wireless communication range of one or more neighboringnode devices located in a corresponding local neighborhood. The nodedevice includes radio communications circuitry, and a controllerinterfaced with the radio communication circuitry. The controller has aprocessor and a non-transitory data storage medium containinginstructions executable on the processor, that, when executed, cause thecontroller to implement a communication mode control module.

The communication mode control module causes the radio communicationscircuitry to selectively operate in the short-range (SR) communicationmode, and in the long-range (LR) communication mode, where the SRcommunication mode utilizes a higher data rate than the LR communicationmode for any given communication bandwidth. The communication modecontrol module controls operation of the radio communications circuitryto (a) advertise connectivity link availability for neighboring nodedevices, and (b) selectively initiate a link in response to connectivityavailability advertised by at least one neighboring node device.

The operation of (a) is performed in both, the SR communication mode,and the LR communication mode, according to a periodicity that isdynamically-variable in response to prevailing circumstances in thelocal neighborhood. The operation of (b) is selectively performed in oneof either the SR communication mode or the LR communication mode, basedon selection criteria that include data throughput performanceassociated with different neighboring node devices with whichconnectivity is available via a certain communication mode. The selectedmode may also be determined by the availability of a particularapplication service accessible via a particular network node.

In a related aspect of the invention, a method for operating a nodedevice is provided for use in a self-organizing wireless multihopnetwork containing a plurality of node devices and at least one gatewaydevice, each node device being within wireless communication range ofone or more neighboring node devices located in a corresponding localneighborhood. The method includes performing communications in ashort-range (SR) communication mode, and in a long-range (LR)communication mode. The SR communication mode utilizes a higher datarate than the LR communication mode for any given communicationbandwidth. Connectivity link availability is advertised for neighboringnode devices, and a link is selectively initiated in response toconnectivity availability advertised by at least one neighboring nodedevice.

Advertising the connectivity is performed in both, the SR communicationmode, and the LR communication mode, according to a periodicity that isdynamically-variable in response to prevailing circumstances in thelocal neighborhood. Initiation of the link is selectively performed inone of either the SR communication mode or the LR communication mode,based on selection criteria that include data throughput performanceassociated with different neighboring node devices with whichconnectivity is available via a certain communication mode.

Advantageously, in the dynamic adaptive, multi-hop mesh environment, andoperation thereof, facilitated by aspects of the invention, nodes areable to continually assess the neighbor environment independent of thecommunication modes used by different neighbors. This capability ensuresthat the self-organizing, self-adapting nature of the network ismaintained even where single and dual-mode nodes are part of the samenetwork. A number of other advantages will be apparent from the DetailedDescription that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1A is a network topology diagram illustrating an exemplary wirelessmultihop network in which embodiments of the invention may be applied.

FIG. 1B is a diagram illustrating aspects of RF multi-hop meshconnectivity in which data network communications paths are establishedby selection among alternative neighbor links, according to certainaspects of the invention.

FIG. 1C is a diagram illustrating a comparison of short-range (SR)long-range (LR) communication modes for some of the node devices shownin FIG. 1A, according to one embodiment.

FIGS. 1D and 1E illustrate multi-modal operation of a node using both,the SR, and LR, communications modes according to various embodiments.

FIG. 1F is a diagram illustrating multi-mode nodes applying the LRcommunications mode for communications to the gateway device forpurposes of connectivity to and from the gateway for a given applicationservice, even where alternative modes may apply for general datatransfers between the nodes and the gateway, according to oneembodiment.

FIG. 2 is a block diagram illustrating parts of an exemplary node deviceaccording to one embodiment of the invention, including a radio circuit.

FIG. 3 is a block diagram illustrating parts comprising the controllerof the exemplary node device of FIG. 2, including a data storage mediumwith program instructions and operational parameters.

FIG. 4 is a block diagram illustrating exemplary functional modules ofthe radio circuit of FIG. 2.

FIG. 5 illustrates some of the functional modules of the exemplary nodedevice of FIG. 2, including a communications mode control module, and acommunications mode parameter setting module, according to oneembodiment.

FIG. 6A is a block diagram illustrating an exemplary structure ofmodules implementing the LR mode as part of the communications modecontrol module of the embodiment of FIG. 5, according to one embodimentof the invention.

FIG. 6B is a block diagram illustrating an exemplary structure ofmodules implementing the SR mode as part of the communications modecontrol module of the embodiment of FIG. 5, according to one embodimentof the invention.

FIG. 7 is a block diagram illustrating an exemplary structure of modulesthat make up a scheduler module of the communication mode control moduleof FIG. 6, according to one embodiment.

FIG. 8 is a block diagram illustrating an exemplary structure of modulesthat make up the communications mode parameter setting module of theembodiment of FIG. 5, according to one embodiment of the invention.

FIG. 9 is a flow diagram illustrating a process of autonomouslyselecting a communications mode, to be carried out by a multi-modal nodedevice, based on availability, application, and performance criteria,according to an embodiment.

FIG. 10 is a flow diagram illustrating a process for selecting acommunications mode based on a preference for using short-range,high-data rate communications, according to an embodiment.

FIG. 11 is a flow diagram illustrating a process for selecting acommunications mode based on performance criteria, according to anembodiment.

FIGS. 12A and 12B illustrate various communication exchanges between anode device and its neighbors.

FIG. 13 is a table illustrating sets of predefined communicationsparameters that are defined based on selected channel bandwidth andspreading factor, according to one embodiment.

FIGS. 14A-14C illustrate exemplary control and message frame formats tobe used with a long-range communication mode according to embodiments ofthe invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A multihop network is one where node devices transmit data messages toone another, including, where necessary, through intermediate nodedevices that can act as routing devices for purposes of relaying datamessages towards their final destination. The destination can be anendpoint node device on the local network, or a gateway node device thatprovides a connection between the local network and another network. Awell-known example of a multihop network is the radio frequency (RF)mesh network topology. Embodiments of the invention may be used in avariety of applications involving data communications. One suchapplication is in energy metering, such as a RF mesh advanced meteringinfrastructure (AMI) network that can provide utilities with a singleintegrated-mesh network for electric, water and gas data communicationswith the ability to support multiple meter vendors and multiple utilityapplication services (including demand response, DR, and distributionautomation, DA). However, it should be understood that the principles ofthe invention are applicable in a variety of different applicationnetworks besides energy metering.

In an exemplary implementation, a radio communications system for dataexchange between wireless network nodes operates in an industrial,scientific, and medical (ISM) radio band. ISM bands areinternationally-recognized portions of the radio spectrum that arereserved generally for RF communications in either licensed, orunlicensed mode, according to the applicable regulatory limitations ontransmission power, transmission duration, and spectrum utilization.

FIG. 1A is a diagram illustrating an exemplary wireless multihopnetwork. Endpoint node devices N₁-N₄ act as sources and destinations ofdata to be communicated, as well as potential relays of data to beforwarded to its destination. Gateway node device GW provides aconnection between the local network and another network. The areasshown in broken lines represent the radio ranges for the various nodedevices and can each be considered as a local neighborhood for theassociated devices. Those node devices which are within radio range arereferred to herein as neighboring devices or, simply, neighbors. Thus,devices N₁ and N₂, within communications range of each other, areindicated respectively by reference numerals 100 and 150.

In data collection systems, such as AMI systems, although data may besent from any node to any other node, and although commands can be sentdown from the gateway GW to one or more node devices, the majority ofthe application service data flow is between the node devices and theirassociated gateway device GW. Neighboring node devices can thus beviewed hierarchically relative to the gateway device GW. Intermediarynode devices through which communications must pass in order to reachthe gateway GW can be viewed as parent nodes, whereas the downstreamnode devices can be referred to as child nodes. That is, along themulti-hop communications path between a node and the GW the nodeneighbor that is ‘closer’ (along the formed routing path) to the GW willbe a ‘parent’ node to the connected neighbor device that is (one hop)farther away.

The radio range depicted in FIG. 1A is limited such that only nodedevice N₁ can create a direct link to the gateway device GW. Nodedevices N₂ and N₃ are therefore children of parent node N₁. Similarly,node device N₄ is a child of node devices N₂ (and a descendant of N₁).Node device N₄ can thus have messages sent along route N₂->N₁->GW forcommunications with the GW.

FIG. 1B illustrates an extended network in which an additional node N5is deployed. Based on the established routing path connectivity betweennodes and the GW, node N₄ is connected to the GW through the parent N₂,but also has the potential for connectivity through an alternative linkconnection to neighbor node N₅ if node device N₂ becomes unavailable oroperates with a reduced performance (as measured, for example, by datapath throughput). Reduced performance can be caused by a variety ofconditions. For instance, the link to from N₄ to N₂ may become lessreliable due to temporary or permanent obstructions or signalinterference. Similarly, the link from N₂ to N₁ may become degraded.Node device N₂ may also be serving a large number of other children, sothat in time-multiplexing communications with its children the potentialthroughput availability that node device N₄ receives may be effectivelylowered. Also, node N₂ may have a higher loading factor due to otherapplication processing tasks, such that it's computing capacity isreduced, thereby limiting its effective communicating availability. Aset of metrics referred to as link cost, and path cost, which can beapplied to derive a measure of data communications throughput can beused to numerically represent the performance of certain neighbors indelivering messages. These may be applied ahead of the device loadingtype metrics. A variety of other measures of node and link performanceare well-known, including received signal strength indications (RSSI),expected transmission count (ETX) for measuring link cost, hop counts,etc. can be applied individually or collectively in measuring path costused to influence connectivity choices across the network. As usedherein, the terms link cost, or path cost, are meant to encompass anysuitable approach for measurement of neighboring node connection orrouting path performance, respectively, whether presently known, orlater-developed.

FIG. 1C is a diagram illustrating a comparison of short-range (SR) andlong-range (LR) communication modes. The radio communication rangedepicted in FIG. 1A is denoted SR in FIG. 1C. A second radiocommunication mode, LR, is depicted in FIG. 1C, and shown in dashedlines. As its name implies, communication mode LR has a greater reachthan mode SR. In the example shown, node devices N₂, N₃, and N₄, as wellas gateway device GW, are capable of dual-mode operation, meaning thateach of these devices can operate selectively in one of either of themodes LR or SR. Node device N₁ is a SR-only device. As can be seen inFIG. 1C, using LR mode, node devices N₃ and N₂ can connect directly togateway GW, without requiring a multi-hop connection throughintermediary node device N₁. Node N₃ and N₂ can also connect to eachother directly in LR mode, without requiring a multi-hop connection.Node device N₄ can connect to node device N₂ through either mode and mayalso be able to directly connect to GW in LR mode. Note that where twonodes are SR mode neighbors they are also potential LR mode neighborswhere both nodes support SR and LR mode communications capability.

FIGS. 1D, 1D, and 1F illustrate multi-modal operation of network nodesusing both, the SR, and LR, communications modes according to variousembodiments. As depicted in FIG. 1D, node device N₁ connects to gatewaydevice GW, and operates as a parent to node devices N₂. Notably, thecommunications with node device N₂ is via SR mode 160, while node deviceN₃ has the option of directly connection to the GW via LR mode 162 orusing a multi-hop SR mode connection via N₁. Based on the examplerouting path connectivity depicted, the path performance criteriadictates that node N₃ connect directly to the GW in LR mode rather thanusing the SR mode connection through node device N₁. For all datatransfers or other communications exchanges between N₃ and N₁, the SRmode (as the only one supported by N₁) is used. In the example depictedin FIG. 1E, node device N₁ connects with gateway GW via SR mode 160,while node devices N₂ and N₃ directly connect to the GW using LR mode162. Even as node N₂ connects to the GW using LR mode, it supportsconnectivity of node N₄ as a child node using a SR mode connection. Ineither of these examples in FIGS. 1D and 1E, N₁ can be a child node of aparent node device (not shown), rather than being a first-level nodedevice with a direct connection to gateway GW as shown. In the exampledepicted in FIG. 1F, node devices N₂, N₃ and N₄ use LR mode for directlyconnecting to the GW for purpose of accessing a specialized applicationservice (such as alarm or status messaging) that is available using LRmode communications. In this example, the LR mode is preferentiallyselected for this application-specific purpose even though the SR modeis otherwise available for use.

In one embodiment, the SR mode utilizes a frequency-hopping spreadspectrum (FHSS) technique and associated transmission modulation thatoffers relatively higher data rates than the LR mode for a givenbandwidth and transmission power. Where link budget permits, nodes areable to apply higher order modulation to increase their transmissiondata rates. Typically, the FHSS operation is based on a quasi-randomfrequency hopping among a set of available channels in the ISM bandbeing utilized. For instance, particular systems operate using fifty 500kHz channels in the 915 MHz ISM band, the 2.4 GHz ISM band, or the5.7/5.8 GHz ISM band.

The LR mode according to this embodiment utilizes a direct-sequencespread spectrum (DSSS) technique, that along with associatedchannelization offers improved link margin over the SR mode, though atthe cost of reduced data rate for a comparable transmission bandwidthand transmission power. To illustrate, in one embodiment, the SR modeprovides data rates of hundreds of kbps, with typical communicationranges of hundreds of meters to kilometers at a transmission power of 1Watt (as permitted by FCC ISM band operating specifications) based onthe given propagation environment. By comparison, the LR mode, accordingto various configuration settings in one embodiment, supports data ratesranging from hundreds of bps through a few tens of kbps. However, theincreased link budget of the LR mode allows communications at muchgreater distances in the range of kilometers to greater than tenkilometers at the same transmission power and operating in the same ISMfrequency band and propagation environment.

In one type of embodiment, the LR mode uses frequency hopping in mannersimilar to that applied in SR mode. Accordingly, the LR mode of thisembodiment utilizes a pseudo-random frequency hopping operation acrossmultiple channels while applying DSSS mode transmission within eachutilized channel. The channels utilized conform to those defined for theFHSS system operation. In one embodiment, the addition of DSSStransmission within the FHSS-defined channel does not widen thebandwidth requirement; rather, for the DSSS mode transmission is adaptedto the defined FHSS channel bandwidth. The advantage of this trade-offis that the additional overhead provided by the DSSS chips improves thelink margin of the LR mode transmission such that, for a giventransmission power, greater transmission range can be achieved whilesimplifying the integrated system operation through the use of a commonset of channels for both system modes.

Applied together in a single network according to embodiments of thepresent invention, selectable SR/LR operation made possible by dual-modeendpoint devices offers greater flexibility and adaptability in networkconnectivity by allowing wider tradeoffs between communications datarates and transmission ranges that can be supported between nodeneighbors with a single mode system. Advantageously, a node device canachieve maximum data rates using SR mode when communicating with nearbyunobstructed neighbors while connecting over longer ranges at lower datarates using the LR mode when other closer-range connectivity does notexist, or when a LR mode is preferred for application-specificconnectivity or to meet certain performance optimization requirements.Furthermore the integrated system allows support for specialized singlemode devices even in a self-organizing network of dual mode SR/LRdevices.

FIG. 2 is a block diagram illustrating portions of node device 100. Nodedevice 100 includes radio communications circuit 202 having transmitterand receiver portions. In one example embodiment, which is described ingreater detail below, the radio circuit includes both, a FHSS radiomodule, as well as a DSSS radio module. In one embodiment thesefunctional modules may be firmware-controllable capabilities of a commonradio device. Data source 204 is that portion of node device 100 whichis served by radio communications circuit 202, and provides any one ormore of a variety of primary functions of node device 100 besides thecommunication function. For example, in an AMI application, data source204 may be an application processor that interfaces to a utility meteror may be a utility meter itself. In an industrial control application,data source 204 may be an instrument, sensor, or actuator; in aninformation technology application, data source 204 may be a computersystem.

Controller 206 oversees and coordinates functionality of radiocommunications circuit 202 and, in some architectures that integrate thecommunications portion and data source portions of node device 100,controller 206 controls the operation of data source 204. In otherembodiments, data source 204 can have its own controller. In oneembodiment, controller 206 includes processing hardware, such as one ormore processor cores, memory units (volatile, non-volatile, or both),input/output facilities, data bus, and other such processing-relatedcomponents. Controller 206 also includes software 208, which in variousembodiments can include an embedded system, an operating system, devicedrivers, and other system code. In addition, software 208 includesapplication-level code that defines the higher functionality of nodedevice 100, including operation of the communications and softwareupgrade modules detailed herein below. Interface circuit 210 facilitatesinput and output of application and control data between radiocommunications circuit 202 and data source 204 according to theembodiment depicted in FIG. 2. In one embodiment, interface circuit 210includes a digital to analog (D/A) or analog to digital (A/D) circuit,or both. In related embodiments, interface circuit 210 can include oneor more of: a bus circuit, a serial port, a parallel port, or anycombination thereof.

Power supply circuit 212 provides electrical power for use by the othercircuitry of node device 100. Various circuitry may have different powerrequirements, such as different supply voltages, source or groundisolation, or the like. Accordingly, power supply 212 provides theneeded power requirements. In one embodiment, power supply circuit 212includes the energy source, such as a battery, for example. In otherembodiments, power supply 212 includes a power capture circuit such as aphotovoltaic cell, for example, or an electrical generator circuit. Instill other embodiments, power supply circuit 212 relies onexternally-supplied power, such as from an AC mains source, and convertsand conditions that power to the various supply taps for the otherportions of node device 100.

FIG. 3 is a block diagram illustrating some of the components ofcontroller 206 according to one embodiment. Controller 206 includesprocessor 214, which includes such parts (not shown) as a control unit,an arithmetic/logic unit (ALU), registers, cache memory, and the like.Processor 214 can include a single or multi-core processor of anysuitable architecture (e.g., RISC/CISC), a microcontroller withintegrated additional components, a digital signal processor (DSP), etc.Processor 214 is interfaced with data storage 216, which can take any ofa variety of suitable forms, and their combinations. For example, RAM,electrically-erasable programmable read-only memory (EEPROM)—e.g.,Flash, disk, and the like, or a combination thereof. In the case of amicrocontroller embodiment, some of the data storage 216 may beintegrated with the control unit and ALU, and other components, asrepresented by the partial overlap of these blocks in FIG. 3. Some partsof the data storage 216 may be situated externally to the processor 214.Input/output facilities 218 include circuitry such as a system businterface that permits interfacing with other components of node device100, including some portions of data storage 216 (such as the case withan external flash device interfacing via system bus).

Also depicted in FIG. 3 is an exemplary organization of content withindata storage 216 according to one embodiment. In this example, datastorage 216 includes a non-volatile memory devise, such a flash device220, which may be part of a microcontroller embodiment of processor 214,or external to processor 214. Flash device 220 stores the executablecode of software 208, along with operational parameters 209, and othervariables that may be stored in the course of execution of software 208.Data storage 216 may also include a random access memory (RAM) device222, which may be used to store parts (or all) of executable code 208for faster access during execution, as well as “scratchpad” memoryspace.

To implement an extensive set of functions, controller 206 operatesunder the control of the program instructions of software/firmware 208.In this regard, each part of the functionality may be viewed as anoperational module. In general, the term module as used herein means areal-world device, component, or arrangement of components implementedusing hardware, such as by an application specific integrated circuit(ASIC) or field-programmable gate array (FPGA), for example, or as acombination of hardware and software/firmware, such as by amicroprocessor system and a set of instructions stored on anon-transitory storage medium to implement the module's functionality,which (while being executed) transform the microprocessor system into aspecial-purpose device. A module can also be implemented as acombination of the two, with certain functions facilitated by hardwarealone, and other functions facilitated by a combination of hardware andsoftware. In certain implementations, at least a portion, and in somecases, all, of a module can be executed on the processor core(s) ofcontroller 206, or in other circuitry (e.g., radio 202). Accordingly,each module can be realized in a variety of suitable configurations, andshould not be limited to any particular implementation exemplifiedherein.

The operational modules in one example embodiment, include suchoperations as communications (including forming message packets,forwarding messages addressed to other devices, message routing, errordetection/correction, packet framing, following communications protocol,etc.), operation of data source 204, various security-relatedoperations, receiving and processing commands, performing softwareupgrading-related operations, and others.

Table 1 below lists a set of abstraction layers that implement majorportions of the communications functionality according to oneembodiment. Although the abstraction layers describe a softwarearchitecture, it should be noted that the software architectureconfigures the controller hardware into a plurality of functionalmodules.

TABLE 1 Exemplary Abstraction Layers Layer Data unit Primary function(s)Application Data Network process to data source Network PacketPacketization of data; routing path determination; neighbor managementRadio Abstraction Interface (RAI) SAR Segment Segmentation andreassembly of packet segments MAC Frame Coordination of the link statebetween two devices, including when link access may and may not occur;frame level , authentication and data reliability. Link Frame Parsingand packing frames; connection/synchronization, reliable data delivery,communication mode selection and implementation

The application layer provides the communication system interface fordata source 204. Accordingly, the application layer processes and passdata from data source 204 to be transmitted via radio communicationscircuit 202, and provide data received to data source 204 in theappropriate format. The network layer serves the application layerprimarily by packetizing data for transmission. Packets generallycontain portions of the data as a payload, and further include controlinformation for routing the packet and reassembling the data itcontains. In this exemplary implementation, routing is performed at thenetwork layer. Neighboring node management and information maintenanceincluding associated neighbor link statistics is supported as asub-function of the network layer. The radio abstraction interface (RAI)translates standardized function calls by the network layer toradio-specific or protocol-specific instructions for lower layers, andvice-versa. This allows the application and network layer codes to beuniversal to all radios and protocols which support the RAI.

The segmentation and reassembly (SAR) layer applies further coding topackets and, in some implementations, further divides the packets.Different SAR processing may apply respectively according to the radiotransmission mode in which the node device is currently operating. Themedium access control (MAC) layer coordinates the link state between twodevices, including when link access may and may not occur. In oneembodiment, the MAC layer maintains a link connection state machine andinsures the reliable delivery of data traffic via ACK/retransmissionprocedures. In a related embodiment, the MAC layer provides themechanism to insure that the link is properly authenticated and lays thebasis for establishing encrypted communications before data traffic isallowed to traverse the link. These functions may differ according toradio transmission mode.

The link layer provides lower-layer services to the MAC layer. In onesuch embodiment, the link layer handles the details of the link layerprotocol, including parsing and packing the data messages into frames.In addition, link layer implements the connection/synchronization andreliable data delivery procedures. As part of carrying out thisfunctionality, in multi-mode node devices, the link layer alsodetermines which mode to use in communicating with specific nodedevices, and performs the necessary operations to carry out thatfunctionality.

In certain embodiments, messages that are communicated between nodedevices are generally sent using a connection-oriented protocol in whichthere is a handshaking process of negotiation between node devicesbefore normal communication over the channel begins. Handshakingdynamically sets parameters of a communications channel establishedbetween the two node devices. It follows the physical establishment ofthe channel and precedes normal information transfer. Typically, thisfunctionality is handled at the lower layers (i.e., MAC or link layer).Connection-less data transfers, where messages can be directly sent orreceived without the establishment of a dedicated radio connection, mayalso be supported by the link layer.

FIG. 4 is a block diagram illustrating exemplary functional modules ofthe radio communications circuit 202 of FIG. 2 according to oneembodiment. Radio communications circuit 202 implements a FHSS module230, which is configured to modulate and demodulate data to betransmitted and received, respectively, via (short range) FHSS mode.Similarly, (long range) DSSS module 232 is configured to modulate anddemodulate data to be transmitted and received, respectively, via theDSSS mode. For transmission, the baseband data to be transmitted ispassed to data input module 324, which buffers the data and provides thedata in suitable segments to either the FHSS module 230, or the DSSSmodule 232. In certain embodiments, data input module 234 may furtherencode the input data to apply certain signaling, a layer of security,or some combination thereof.

Transmission/reception mode selection input module 236 receives an inputindicating the type of spread spectrum modulation to be used from amongFHSS and

DSSS for both data transmission and when the device is in receptionmode. Accordingly, transmission mode selection input module 236instructs FHSS module 230 and DSSS module 232 to act on the datareceived by data input module 234. In embodiments where the DSSS mode isapplied in conjunction with frequency hopping, the DSSS module 232processes data to be transmitted together with applicable instructionfor implementing specified channel hopping.

Data transmission module 238 is configured to transmit the modulatedsignal according to the transmission protocol. For FHSS mode, datatransmission module 238 receives a frequency hopping instructionsequence from FHSS module 230 that indicates the transmission frequencyfor each consecutive FHSS channel. Data transmission module 240 providesthe carrier signal at the specified frequency, modulates the carrieraccording to the defined modulation scheme—e.g., PSK, FSK, ASK, QAM,etc. amplifies the modulated carrier according to specified transmissionpower (which may be variable in certain embodiments), and feeds thissignal to an antenna for wireless transmission. Data receiving module240 is configured to receive transmitted signals using inverseoperations in the reverse order to those taken by data transmissionmodule 238. The demodulated baseband signal obtained by operation ofdata receiving module 240 in conjunction with FHSS module 230 and DSSSmodule 232 is provided to data output module 242, which buffers thereceived data and makes it available to be read and acted upon.

Referring now to FIG. 5, some of the modules of an exemplary node device100 a according to one embodiment are illustrated. In the embodimentshown, node device 100 a includes controller 206 a with which modules402-418 are realized. Data source interface module 402, which may beregarded as operating primarily at the application layer, exchanges rawdata with the data source portion. Networking module 404, operatingprimarily at the network layer, performs packetization of data androuting functionality including maintaining neighbor information thatidentifies the transmission mode for connection with each associatedneighbor. There are many known routing techniques, e.g., De Couto,Douglas S J, et al., “A High-Throughput Path Metric for Multi-HopWireless Routing,” Wireless Networks 11.4 (2005) at 419-434,incorporated by reference herein. Embodiments of the inventioncontemplate that any one or more of a variety of suitable routingtechniques, whether known, or arising in the future, may be utilized.

Link layer module 406 interfaces with the radio circuit and operatesprimarily at the link layer, carrying out the link layer operationsdescribed above according to the particular transmission mode operatingat the given time. Monitoring module 408 monitors one or moretransmission performance parameter, such as retransmissions, ACKs sent,failures to receive ACKs, data rate achieved, or other such observableparameter. This monitoring is performed based on transmissions sentusing a connection-oriented protocol. For connection-less data receptionthe monitoring can take the form of measured received signal strength(RSSI), for example.

Statistics module 410 collects multiple samples of the transmissionperformance parameter values obtained by monitoring module 408, andperforms a statistical summary of those multiple values. In oneembodiment, the statistical summary represents a statistical summary,such as an average value, median value, or most frequent value. In arelated embodiment, the summary statistic is weighted, for instance, arunning average with greater weight attributed to more recent values.

Link cost appraisal module 412 performs the computation of link costbased on the statistical data for the actual communications links. Inone type of approach, the link cost is defined as a throughput metric,such that its value represents the radio communication performanceassociated with the particular neighbor device serviced by the link. Invarious embodiments, a plurality of different metrics are combinedformulaically to obtain the throughput metric.

The link cost value is passed to routing table management module 414,which updates the routing information according to the predeterminedlink cost-based algorithm for routing. Networking module 404 makesreference to routing table management module 414, and performs updatesof the routing tables as needed. In delivering data messages, thewireless network of FIG. 1 performs a dynamic routing scheme. Link costinformation is passed to and maintained by the neighbor managementmodule 419, which also keeps track of the applicable transmission modeto the particular neighbor node.

Communication mode control module 416 determines the communication modeto be used for initiating a communication session with each individualneighbor, and for monitoring the airwaves for the presence of on-aircommunications to be received. As will be described in greater detailbelow, the communication mode control for each individual transmissionis based on a communication mode control routine that takes into accounta number of factors, including the availability or unavailability ofcommunication modes, application requirements, and overall communicationperformance for the available communication modes. Communication modeparameter setting module 418 further specifies, for the selectedcommunication mode, which variable parameter values to use for thepresent operation. For instance, in a given LR communication mode, theremay be different data rates or different spreading factors from which toselect for creating a LR mode transmission. Accordingly, communicationmode parameter setting module 418 determines, based on its selectionlogic and on the prevailing circumstances, which parameter values toapply to a current transmission.

FIG. 6A is a block diagram illustrating an exemplary structure of LRmode modules that make up communications mode control module 416according to one embodiment. Communications mode control module conductstwo types of operations: beacon operations, andconnection/connection-less data communications operations. As will bedescribed in greater detail below, these two types operations aretime-multiplexed according to a schedule (with the schedule beingdynamically variable according to the prevailing circumstances in thenode device's neighborhood according to one embodiment). In general,discovery beacon messages are broadcast at a variable interval toidentify the presence of node device 100 a to neighboring nodes.Associated-neighbor beacons are sent out more frequently to supportassociated neighbor synchronization and provide low-latency periodicconnection establishment access opportunities when a node has associated‘child’ node neighbors that use the parent for access to the networkusing LR mode. In one type of embodiment, which is described in greaterdetail below, each beacon message is associated with a transmissionframe structure in which a series of receive time slots follow thebeacon message transmission (see FIG. 14). During the receive timeslots, the node device that transmitted the beacon listens forconnection request messages sent by neighboring nodes in response to thebeacon message, to initiate communications. The connection requestmessages are part of the connection operations. The receive slots mayalso be used by neighbors to send connection-less data messages to thenode transmitting the beacon.

FIG. 6B is a block diagram illustrating an exemplary structure of the SRmode modules that make up communications mode control module 416according to one embodiment. Communications mode control module conductstwo types of operations: beacon operations, andconnection/connection-less data communications operations. In the caseof SR mode associated neighbors can initiate connections without theneed for a dedicated Associated-neighbor access beacon/synchronizationtransmission.

Beacon operations are handled by SR beacon module 420 a and LR beaconmodule 420 b, for SR communication mode and LR communication mode,respectively. Connection-oriented and connection-less operations arehandled for SR and LR communication modes, respectively, by SRconnect/connection-less module 422 a and LR connect/connection-lessmodule 422 b. Each of the beacon modules 420 a, 402 b has acorresponding discovery beacon module 424, while the LR mode alsoincludes the associated-neighbor beacon module 426 for synchronizationand ensuring faster connection and message transfer access when thereare known, associated LR mode neighbors. Each discovery beacon module424 defines functionality facilitating discovering (or being found by)neighboring nodes. This can include transmission of advertisingmessages, such as beacons, on a dedicated control channel or acrossmultiple frequency channels (in the case of SR, FHSS mode) at a definedrepetition rate. In one embodiment, the repetition rate is dynamicallyvariable, but is always set to a minimal, nonzero, rate, meaning thereis some minimum new neighbor finder beacon activity, even in thepresence of numerous established neighbors. In other embodiments, therepetition rate is fixed at a configured rate, which can be varied via aconfiguration process, but is otherwise not automatically adjusted inthe absence of a specific adjustment command.

Each LR mode associated-neighbor beacon module 426 facilitatesestablishing communications with the already-established (i.e., known)LR mode neighboring nodes of node device 100 a. This functionalityincludes broadcasting beacons according to the defined frequency hoppingschedule, at a dynamically-determined repetition rate that is greaterthan the repetition rate of the discovery beacons sent by the discoverybeacon module 424 whenever the transmitting node has associated ‘child’node neighbors. If there are no associated ‘child’ neighbors only thediscovery beacon may be transmitted.

Although for LR mode the beacons sent by the discovery beacon module 424a and associated-neighbor module 426 a may have different packetstructures and data formats in various embodiments, in one particularexample embodiment, the general packet structure and message format arethe same.

Each of the SR and LR connect/connection-less modules 422 a, 422 bincludes a connection module 428 and a connection-less module 430. LRmode connection module 428 b monitors the control channel beacons of itsparent or its own associated-neighbor beacon requests, and establishesconnections with neighbors that are new (i.e., not present on the nodedevice's list of neighbors) or known and already having existingneighbor associations. Connection-less module 430 facilitatestransmission and reception of messages from new or known neighbors.

In one embodiment, the LR mode beacon operations are performed by nodedevices operating in their capacity as parent nodes, or potential parentnodes, and the connect operations (responsive to received beaconmessages) are performed by the node devices when operating in theircapacity as child nodes. According to this approach, a child node thathas a message to be transmitted toward the gateway waits for a beaconmessage from its parent before a connection can be established. Inanother type of embodiment, beacon messages are sent by node devicesthat have a message ready to be transmitted, in one of either LR or SRmode regardless of their relative hierarchy to gateway devices.

In one embodiment, the following operations are handled bycommunications mode control module 416:

-   -   SR communication mode, beacon operation, new neighbor;    -   SR communication mode, beacon operation, existing/known        neighbor;    -   SR communication mode, connect operation, new neighbor;    -   SR communication mode, connect operation, service existing/known        neighbor;    -   SR communication mode, connection-less operation;    -   LR communication mode, beacon operation, new neighbor;    -   LR communication mode, beacon operation, existing/known        neighbor;    -   LR communication mode, beacon operation, connect operation, new        neighbor;    -   LR communication mode, beacon operation, connect operation,        existing/known neighbor; and    -   LR communication mode, beacon operation, connection-less        operation.

According to certain aspects of the invention, these operation modes aretime-multiplexed in node device 100 a. Scheduling module 432 defineswhen, and if, each of the operations is to be activated, and can furtherdefine the schedule of tasks that are part of each of the operations tobe carried out. Clock module 434 provides a time reference to the sothat the operation schedule defined by scheduling module 432 can befollowed.

Scheduling module 432 exchanges information with communication modeparameter setting module 418. Based in this exchange, the schedulingamong the various operations and their constituent tasks is varied.Inputs that affect the parameter setting include the neighbor table, therecent history of communications with neighbors, applicationrequirements, and the like. A variety of combinations of factorsincluding these, and other, inputs, are contemplated in variousembodiments for adjusting the schedule. For example, if node device 100a has a relatively larger number of children, it may be beneficial forthe sake of improving overall data throughput in the neighborhood tohave node device 100 a spend a greater share of time in beaconoperation, existing neighbor operations so that a greater number ofchild nodes can be serviced in a given operation cycle.

According to various embodiments, the SR and LR communication modes areadministered according to different protocols. For instance, in networkneighborhoods where the node devices have already establishedrelationships with their neighbors, a node device operating in the SRcommunication mode that has a message to send simply can broadcastsmessage connection request, and re-broadcasts the request until anacknowledgement is received from the neighbor device for which themessage was intended. The re-broadcasting can follow the establishedFHSS channel sequencing. This type of SR communications protocol can beused in embodiments where there is sufficient channel capacity andoperational capability of the node devices to re-transmit messages onthe one side, and to listen for messages on the other side, withsufficient periodicity, such that messages can be communicated withinacceptable communication performance limits. In this embodiment, the SRbeacons and connections in response to the SR beacons are used to findand establish connectivity to new neighbors, but not for routinecommunications with known neighbors. In related embodiments, the LRcommunication mode is used less frequently, such that communications canbe established only through a beacon-response protocol, even with knownneighbors.

According to one aspect of the invention, each node device independentlydetermines its scheduling of operations in each of the communicationmodes. Taken collectively, all of the node devices in a neighborhood,and indeed, in the network, achieve a self-organizing multi-hop networkthat does not require a centralized system coordinator. As part of theindependent determination of communication mode operations, each nodedevice selects a communication mode from among the SR and LR modes forconnecting to a neighboring node or to make itself available to receivefrom an existing or potentially new neighbor. Different circumstancescan give rise to different selections of SR/LR communication modeoperation ratios, even when connecting to the same neighboring device.In one embodiment, selection of communication mode is based on a regularre-assessment of the available neighboring nodes that can be parentnodes, the data throughput available to the nearest gateway devicethrough each of the potential parent nodes (which itself can be afunction of link quality, neighboring node performance, and other suchfactors), and application requirements (such as preferences as tocommunication latency versus data throughput for a particular service).

According to one embodiment, each dual-mode node device provides beaconoperation in both communication modes, SR, and LR. In a relatedembodiment, the ratio of SR-LR beacon operation is independently variedby each node device according to the prevailing circumstances. In oneexample, for a given node device, the ratio of LR to SR beacons can beautomatically varied between 0.01:1 and 1:0.01.

The circumstances according to which the SR-LR operations can be variedfor beacon transmission operations can include whether the node devicehas any child nodes that connect to it via LR mode, how many of suchchild devices there are. In a related embodiment, the history of LRconnections with any of these child devices is also considered,including such statistics as how often the child devices establishconnections in response to the LR beacons, the amount of datatransmitted by each of the child devices, and the like. Thesecircumstances provide indicia of the relative necessity for supportingthe LR mode.

In one embodiment, the existence of even a single child deviceconnecting via LR mode will cause the parent node device to perform theLR associated-neighbor beacon operation to service existing neighbors.Frequent communications via LR mode, as established by the one or morechild nodes in response to the LR beacons sent by the patent node, orrelatively greater amounts of data (each of which can be assessed basedon thresholds or on predefined formulas) are indicators of the need toexpand the LR beacon duty cycle to better support the LR child node(s).Also, the use of certain applications that rely on low-latencyconnections over LR mode may call for increased transmission of LRbeacons.

A lack of child nodes utilizing the LR mode may be responded to by onlyperforming the LR discovery beacon operation, which has a substantiallyless frequent beacon interval to free up more time for SRcommunications, save energy, and keep the channel clear for other nodedevices using the communication band.

In one embodiment, the discovery beacon operation differs from theassociated-neighbor beacon operation in that the operation involvessubstantially more frequent beacon transmissions so that the node isavailable to its known, existing associated neighbors with low latencyhigh availability. In a related embodiment, the LR mode discovery beaconoperation is assigned to a single frequency. For example, the discoverybeacon can be assigned to a particular control channel of a set ofchannels, rather than using all of the available channels in the ISMband in which the node devices operate. In another related embodiment,even when a node services child nodes, it maintains its discovery beaconoperation so that new prospective child nodes can more readily receivethe find new neighbor beacon by virtue of knowing to monitor the controlchannel.

FIG. 7 is a diagram illustrating the modules facilitating an exemplaryportion of the functionality of scheduling module 432, which portion isresponsible for selecting whether to connect to or send connection-lessmessages to a neighboring node via SR connect module 422 a or LR connectmodule 422 b. For an existing neighbor the mode decision may be directlybased on the stored neighbor management data (from module 419). The modeused for a connection to the neighbor is also influenced by the need toevaluate link and network path performance using alternative connectionmodes. Mode control algorithm execution module 440 applies a predefineddecision algorithm to determine the communications mode that is to beused, and provides an output to TX mode select input module 236 and toSR comment module 422 a and LR connect module 422 b. The decisionalgorithm is defined by mode selection criteria, which in turn ismaintained by mode selection criteria storage module 442. Mode decisionupdate module 444 receives criteria update or algorithm execution updateinformation, which may be inputted from a transmission by a systemadministrator via radio communications, or from a field configurationdevice through a local communication port.

In the embodiment depicted in FIG. 7, mode control algorithm executionmodule 440 additionally bases the communication mode selection onvarious inputs that provide information about the prevailingcircumstances including neighbor connectivity and the need to detect orupdate information on the existence of nodes within the neighborenvironment. Mode control may apply in the context of connecting to orattempting to connect to send data to a neighbor. Mode selection is alsomade in the context of a node's idle mode status when it is available tosupport communications, in either mode, with its various node neighbors.Application requirements determination module 450 reads control-relatedinstructions in messages received, or to be transmitted, to determinethe preferred, or required, communications operability to serve theapplication layer functionality. For example, one type of applicationlayer requirement can call for the lowest possible latency fordelivering relatively small amounts of data. This requirement may beassociated with alarm messages, for instance. Accordingly, mode controlalgorithm execution module 440 would select the LR communication modepreferentially.

In another example that calls for the use of the LR communication mode,a geographic location-determining application that measures indicia ofdistance between node devices based on received signal strength ormessage transmission delay benefits from the LR communications mode,which have an improved ability to directly reach, in a single hop, tospecialized reference nodes that may support a position-determination ortime synchronization application.

In a related embodiment, the selection of communication mode is based onthe effectiveness, or communications path performance, of neighboringnode devices through which communications are routed. In accordance withthis approach, link quality determination module 452 assesses theperformance of the communication link with a given neighbor. A varietyof link quality performance measures may be suitable. For example,expected transmission count (ETX), average data throughput rate,received signal strength (RSSI), and the like, may be employed.Performance measures may represented not just the immediate neighborlink but potentially the path performance to a given destination such asthe GW. Neighbor performance determination module 454 assesses otherfactors affecting the communications performance of a neighbor, such asmeasures of relating to latency (e.g., beacon intervals, connectivityperiodicity, etc.). This type of information may be obtainable from acommunication log that stores measures of performance for pastcommunications, or from the routing table stored locally on each nodedevice, which is built and updated continuously as part of the routingdetermination operations carried out by the network layer.

Neighbors may also exchange relevant performance information, such asindicators of loading of the communications overhead. For example, if anode device has many child nodes that it services, it may haverelatively less time to devote to any one child to facilitatecommunications to the gateway node. In one embodiment, an aggregatecommunication performance measurement is provided by data throughputdetermination module 453. This module can provide an indication of theoverall data throughput to the gateway node, for example, over a definedmonitoring time window, that is available for each parent node device.According to one embodiment, a uniform performance metric is adoptedacross the network of node devices to enable a standardized set criteriafor communications performance.

Neighbor hierarchy determination module 456 ascertains the networklocation, or multi-hop level, of each neighboring node relative to thegateway device. The network location in this case can be represented interms of number of hops needed by that neighbor to reach the gateway.This information is indicative of whether a given neighbor node is apotential parent node. In a related embodiment, the communication modethat is currently being used by the neighbor device, SR or LR, can alsobe determined. Depending on the criteria used for mode selection and onthe present needs by a certain application, neighbor hierarchydetermination module 456 can provide essential information on theprevailing network conditions to enable more sophisticated decisioncriteria to be used. For instance, in an embodiment that determines acommunication mode by weighing factors relating to data bandwidth on theone hand and latency on the other, the neighbor hierarchy knowledge canhelp to inform the mode selection decision by providing insight into thespeed or delay performance of each neighbor node.

Neighbor hierarchy determination module 456 can obtain such informationfrom the networking module 404, the routing table management module 414,or via interrogation of each of the neighbor devices using controlmessaging, for example. The determined network location can be anotherfactor that is taken into account by mode control algorithm executionmodule 440 to make the communication mode selection. As depicted, datathroughput determination module 435 can use a throughput metric that issensitive to the neighbor hierarchy, making a separate hierarchydetermination redundant in some embodiments.

History log module 458 maintains information on previous connectionsmade with each neighbor node, and the performance of those connections.This information can also be taken into account by mode controlalgorithm execution module 440. The history log can include such itemsas SR/LR connection mode, data throughput achieved for previousconnections, and the like. History log module 458 can also providestatistical aggregations, such as mean values, median values, variances,etc. The module will receive input data from the neighbor managementmodule 419.

Turning now to FIG. 8, an exemplary structure of modules that make upthe communications mode parameter setting module 418 is depictedaccording to one embodiment. The actual setting of communicationparameters is performed by parameter setting execution module 462. Thismodule applies criteria in making the decision, which is maintained byparameter setting criteria storage module 464. Parameter setting updatemodule 466 receives parameter setting criteria update or algorithmexecution update information, which may be inputted from a factoryconfiguration, from a transmission by a system administrator via radiocommunications broadcast messages, or from a field configuration devicethrough a local communication port.

In the embodiment depicted, parameter setting algorithm execution module418 sets one or more of the following parameters for each of thecommunication modes, LR mode 468 and SR mode 470: control channel dutycycle 472; transmission duty cycle 474, beacon periodicity 476,transmission frame period 478, channel capacity allocation 480,transmission spreading factor 482, and transmission bandwidth 484. In arelated embodiment, the SR communication mode 470 has fixed values forcertain ones of the parameters that are varied for the LR communicationmode 468. In an alternative embodiment, there are certain parametersthat are adjusted in the SR communication mode that are not adjustablein the LR communication mode.

According to one type of embodiment, the communication mode parametersare set based on the requirements indicated by the beacon received fromthe neighboring node to which a connection is to be established. As willbe described in greater detail below, using a common, pre-definedtransmission setting, one or more variable parameters may be dictated bythe beacon-sending node, to which the responding node must adjust inorder to establish communications. In this type of embodiment, parametersetting execution module 462 of the beacon-sending node applies aparameter setting algorithm to define the communication parameter for atleast the LR communication mode. In conjunction with a dedicatedconnection establishment, the parameters can be set differently for usewith each of its child nodes. Common parameters can be set based on oneor more factors including, but not limited to, the number of child nodesthat the node device services, communication performance measured forcommunications with parent or child nodes based on recent history,communication channel availability, the density of node devices in thelocal vicinity, etc.

In one embodiment, the communication parameters to be used are includedas part of a synchronization message content sequence in the header ofthe beacon frame. In another embodiment, this information is includedelsewhere in the beacon frame, such as in a specially-defined field ofthe message payload portion of the frame. In response to receiving sucha beacon, the receiving node decodes the parameter information, andparameter setting execution module 462 of the receiving node adjusts itsparameters to match the parameters specified in the beacon forsubsequent connection-less or dedicate connection assignments.

In a related embodiment, a plurality of parameter values are representedby a single string or numeric value incorporated into the beacon. Thisstring or numeric value is termed a frame parameter (FP). The receivingnode is programmed to derive the plurality of parameter values accordingto a predefined decoding sequence. In one example, a lookup table ismaintained by parameter setting execution module 462 of each nodedevice, which defines various combinations of parameter valuescorresponding to different FP values. In another embodiment, one or moreformulas are applied to generate the FP value from the plurality ofparameter values, and to derive the parameter values from the FP valueas the reverse operation. It should be understood that, in variousembodiments, there may be one FP that defines all of the variableparameter values, or there may be more than one FP value, each of whichdefines one, or a plurality, of parameter values.

FIG. 9 is a flow diagram illustrating an exemplary algorithm, at ahigh-level, for making LR communication mode selection in connecting toa node for which neighbor connectivity did not previously exist,according to one embodiment. At 502, an availability-based modeselection is initiated. This operation involves determining whether SRor LR mode is supported. At 504, it is determined whether any of the twomodes are not available. Accordingly, the available mode is selected forLR mode communications at 506. At 508, once the LR mode is selected, thebeacon listening cycle is updated to match the periodicity of thebeacons of the communication mode. The beacon periodicity can beprovided within the beacon using a FP value, as a dedicated field, or asa tagged value within the payload of the beacon. At 510, thetransmission parameters are updated to match the communicationparameters specified for the beacon.

Where both communication modes are available, the process proceeds to512, where an application-based communication mode selection may beinitiated. The nature of the communication to be transmitted can dictateone or another of the communication modes. At 514, it is determinedwhether there are application requirements for a particularcommunication mode. If that is the case, at 516 the application-specificLR communication mode is selected. Otherwise, the process proceeds toperformance-based communication mode selection at 522.

FIG. 10 illustrates the alternating mode selection of a dual-mode nodeattempting to find initial access connectivity to the network. Thescheduling for moving from one mode to the next is under the controlapplied via the transmission/reception input module 236. In thisapproach, there is a bias for selecting the SR mode to take advantage ofits higher data rate capability. At 630, the node device listens for aSR beacon using a SR receive mode. At 632, it is determined if the SRbeacon was received. In the affirmative case, a selection is made to usethe SR mode to make the connection. Otherwise, at 636, the node devicelistens for the LR beacon using its LR receive mode. If, at 638, a LRbeacon is not detected after a predefined time period, the processrepeats to provide further opportunity to connect via SR mode. If the LRbeacon is received, the LR connection is made at 640.

FIG. 11 illustrates an exemplary process for selecting the communicationmode, when evaluating network connectivity through a givenexisting/known neighbor, based on performance criteria according to oneembodiment. At 642, a connection is made according to the assumedcurrent preferential SR mode. At 644, the data throughput is monitoredfor this mode using one or more performance measures. At 646 the SRperformance is compared against a threshold. This threshold may bedefined, for example, as the best possible LR throughput level. In thiscase, a throughput level that is below the threshold indicates thepossibility that another parent node device, which may be available viathe LR communications mode, might perform better. If the SR performancelevel is above the threshold, SR mode is maintained at 648, and theprocess loops back to monitoring the throughput performance insubsequent future connections (used for message data transmission ofestablished specifically for link/path performance evaluation).Otherwise, if the threshold performance level is not attained, the nodedevice will connect to the neighbor via LR mode at the next opportunityat 650.

At 652 the LR data throughput is checked and a comparison is made at 654as to whether the LR throughput is better or worse than the SRthroughput. If the SR mode performed better, the process loops back toconnecting via the SR mode. If the LR mode is better than thepreviously-measured SR performance, then the LR mode is maintained forsome predetermined amount of time, communication cycles, or until sometriggering event occurs at which point the process determines that theSR mode is worth trying again, as depicted at decision 654. One exampleof a triggering event other than time lapse or communication cycle countis if the received signal strength (RSSI) of a received, alternativeneighbor LR beacon is significantly improved and/or offering a higherperformance connectivity path relative to the current networkconnection. If it is time to try the SR mode again and/or a new SR modeneighbor is detected, the process loops to 642 to reconnect via the SRmode.

FIGS. 12A and 12B illustrate various communication exchanges between anode device and its neighbors in greater detail according to embodimentsof the invention. These examples illustrate a mechanism for categorizingnew and existing neighbor associations according to the communicationmode selected for communications with the particular neighbor. Accordingto one embodiment, each node device assigns a neighbor class of either“primary” or “secondary” for its neighbor nodes. This classification canbe factored in to the frequency of scheduling connections for selectionalgorithm evaluation for the communications mode to the particularneighbor.

According to one embodiment, initially, to join the network upon powerup a node device enters a frequency scanning receive operation in whichit will camp (i.e., passively receive transmissions) on a given systemfrequency. During this SR receive phase the node listens for SR beaconsbeing transmitted by neighbors that are already joined to the network.In this embodiment, only those nodes that are already joined to thenetwork will transmit very low duty cycle periodic SR beacons (repeatedon all operating frequencies in each beacon transmission cycle). The SRbeacons carry node-identifying information as well as network-specificoperating and potential routing-related information.

The joining node remains in the receive operation and will shift fromone frequency channel to the next while remaining in the SR receive modeand continuing to listen for transmitted SR beacons. To provideresilience against interference on any single channel or channels, thenode can shift from one frequency to the next frequency channel acrossthe set defined for the network after a preconfigured receive period oneach frequency. The sequence of frequencies on which the nodeprogressively camps to receive a SR beacon may be random or otherwisesystem-defined. The node continues to cycle in the SR mode receiveoperation from one frequency to the next until all of the operatingspectrum frequencies are covered and will continue to operate in thisstate over multiple iterations of the entire frequency spectrum ofavailable channels.

In one example embodiment, the duration of the SR receive phase is equalto a multiple of the maximum period between SR mode discovery beaconsfor connected nodes, or a system-specified time period. If at any timeduring the receive scanning an SR mode discovery beacon is received, thenode will schedule a connection to the identified neighbor and willattempt to initiate network joining in SR mode.

Once the complete SR receive operation is completed and if no SR beaconshave been received, the node device switches to LR mode. In the LR modereception operation, the node performs a similar cycle of camping on asingle frequency, at a defined default spreading factor (SF), for adefined duration before changing to the next frequency. This issimilarly repeated across a set of defined control channel frequenciesor across the entire operating system frequency spectrum. At eachfrequency, the node device listens in LR mode for beacons transmittedfrom any neighbor node that already has network connectivity.

In a related embodiment, the LR-mode frequency scanning is additionallyperformed over various channel bandwidths pre-defined for the system andacross all of the possible frequency channels associated with each ofthe particular channel bandwidths. In addition, the LR mode receivescanning can be performed for various spreading factors defined for thesystem. In another related embodiment, the time spent camped on eachfrequency channel can be variably based on the maximum beacon intervalwith which nodes that have network connectivity are programmed togenerate a LR mode beacon on a single channel. Preferably, the campingtime at least exceeds this maximum periodicity. Alternatively, the timeduration per frequency channel may be fixed.

If at any time during the receive scanning a LR mode beacon is received,the node device responds by initiating a connection to the identifiedneighbor and attempts to initiate network joining in LR mode. If, afterthe series of LR mode frequency channel and spreading factor receptionscanning cycles that exhausts the full range of possible channels,channel bandwidths, and spreading factors, a LR mode beacon is notreceived, the node returns to the SR mode reception scanning phase.

In this embodiment, after returning to the SR receive mode the node willcontinue in the SR scanning phase for another full cycle duration. Oncethe full SR receive mode scanning period is reached, if no SR discoverybeacons have been received the node will again switch to LR mode channelreception.

A mains-powered node device will continue to alternate between fullcycle periods of SR mode receive scanning and LR mode receive scanninguntil the beacon of a neighbor is found in either SR or LR mode thatallows the node to initiate connectivity to the network. Abattery-powered node device will, after a defined number of alternatingphase periods in each SR and LR reception scanning modes, return to itssleep mode for some predefined extended period during which it will nolonger maintain active reception. This will allow the battery-powerednode to preserve available battery life.

As illustrated in FIG. 12A, an exemplary set of communications exchangesfor a node initially joining the mesh network is depicted. Based on thepassive-join approach described above, the dual-mode node deviceinitiates system access in the high-data-rate SR mode to attempt todiscover neighboring nodes (or Gateways) already connected to thenetwork. Node neighbors already connected to the network indicate theirconnectivity and availability by transmitting periodic, low duty cyclediscovery beacons, such as those described above. In this embodiment,dual-mode nodes broadcast both SR and LR mode beacons while single-modenodes broadcast a beacon in their single operating mode. The duty cyclesof the discovery beacons can be as infrequent less than 0.1% of a node'soperation and can be varied according to the communication mode and thenode's self-discovered neighborhood density.

As depicted in FIG. 12A, the new joining node begins scanning for SRmode beacons. Upon discovery of a neighbor the node schedules aconnection to the neighbor. That connection is used to perform a networkaccess routing exchange and to further evaluate the RF link quality tothe neighbor as well as confirm other network access/control informationthat may have been derived from the discovery beacons. Based on the linkconnection and routing exchange the new node is able to establishnetwork access using the neighbor node as a parent for connectivity tothe network. Network access is established via the gateway devicethrough which the neighbor (parent) node is currently connected. The newjoining node will at this point initiate a discovery exchange with theidentified network gateway to register its presence in the network, tocomplete system security access/authentication, and to obtain anydynamically-assigned network address information. Application serviceinformation related to devices (such as sensors or meters in the case ofan AMI network) that may be associated with the node may also beregistered to the application network server(s) via the new servingGateway.

Once connected to the network, the new node schedules and begins totransmit its own periodic, low-duty-cycle discovery beacon, to bebroadcast in both SR and LR modes where the node is so capable. Thejoining node also continues to monitor for other connected neighborsthat may provide SR discovery beacon broadcasts. As each new neighbor isfound, the newly joining node schedules a connection for purposes ofassessing whether the discovered neighbor can provide better networkaccess connectivity. Because the newly-connected node itself broadcastsdiscovery beacons, its presence may also be observed by a neighbor whomay initiate the neighbor connection (not shown). As part of buildingpotential diversity for network connectivity as well as service access,the new node will also initiate the process of performing low duty cyclebackground LR mode scanning for discovery of LR supporting neighborsthat may provide alternate network connectivity should the quality ofestablished SR mode connectivity degrade or be lost entirely.

As illustrated in FIG. 12A, the already-connected neighbors as well asthe newly joined node, even while connected to the network in SR modewill continue to transmit periodic LR beacons. This operation allows newnodes that are unable to connect to the network via the preferentialhigher-data-rate SR mode to discover node neighbors using the LR mode.It will also facilitate identification of LR mode application-specificavailability. In the illustrated example, the newly-joined node withavailable SR connectivity does not initiate LR mode network connectionsto discovered neighbors. However, as described above, there may be asituation in which all available SR more connectivity performance dropsbelow a threshold, necessitating LR mode connectivity.

For each discovered neighbor, the joined node device assesses theinformation provided in their discovery or associated-neighbor beaconsand, where appropriate (based on the information broadcast), establishesa connection for routing exchange and further network path costevaluation. In this embodiment, the link performance assessment andevaluation of the connectivity path to a serving Gateway are central tothe performance evaluation that a node carries out in deciding whichneighbor and, ultimately, which communication mode to select inconnecting to the network.

In a related embodiment, the path selection performance assessment isprimarily measured by the effective throughput of the associated fullconnection path to a serving gateway. Even if the evaluated neighbordoes not offer a better access path into the network, the neighborinformation may still be maintained for potential future diversity orservice-based connection access. If the discovered neighbor does notoffer a better access path no change is made to the node's currentparent and associated gateway connectivity into the network.

On the other hand, if a better access path is provided through a newlydiscovered neighbor (based on the applied path selection criteria), thenode device updates its network connectivity by changing to the newparent node. If the new parent is associated with a gateway differentfrom the one to which the node was previously associated, an explicitdiscovery update is also made to the new network gateway to which thenode has just attached.

A node device, once connected to the network, will continue to discoverand evaluate node neighbors in SR and LR mode (including evaluationsthat are performed without the need for a dedicated connectionestablishment). The node will update its connectivity by selecting andassociating to any node neighbor where the local link connection to theneighbor as well as the offered network path to a serving gatewayimproves connectivity based on, for example, the routing andnetwork-defined path selection criteria based on the throughput metric.By observing periodic broadcast beacon information and performingtargeted neighbor connection link assessments, a node device willcontinue to maintain and update its optimal connectivity path to thenetwork. Accordingly, in cases where the primary RF link, network path,or physical/environmental conditions change, the node device will beable to use the diversity of SR or LR mode neighbors to optimize theperformance of its connectivity to the network or to driveapplication-specific mode control.

FIG. 12B illustrates an example where a node that may have previouslyhad limited SR mode connectivity through a single neighbor or set ofneighbors and where that connectivity degrades or is lost over time.Having connected to the network in SR mode, the node device will haveestablished connectivity to a serving gateway via a parent neighbor nodein SR mode. If the quality of the available neighbor connectionsdegrades such that the available SR mode access connectivity falls belowa given threshold, the node will seek to establish alternate networkconnectivity using the LR mode where such potential connectivity waspreviously identified. While previously in SR mode the node will haveperformed a long duration periodic low-duty-cycle repetitive scanningthat allowed it to observe and store the presence of LR-mode beacons.The maintained LR-mode neighbor information is used, where applicable,to speed the search for LR-capable neighbors when a network access modechange is called for.

The process for discovery of LR-capable node neighbors is similar to thecase in which a new joining node is unable to find SR neighbors forinitial network connectivity and attempts to access the network byswitching to a dedicated LR mode neighbor search.

In the case of joining the network for the first time, the node will nothave the benefit of LR node neighbor information collected by a nodethat had previously been operational in SR mode. Accordingly, the nodedevice monitors for LR mode visibility beacons, including potentiallythose of previously-observed LR mode neighbors. When LR-capableconnected neighbors are discovered the node attempts to initiate andestablish network connectivity using the LR mode. In addition to thebeacon information that is broadcast, the node will use the establishedconnection and routing information exchange to evaluate the networkconnectivity path offered by their neighbor nodes. As in the case ofSR-mode access, the network access path selection criteria for choosinga discovered neighbor is measured primarily in terms of the datathroughput for the overall path. For performance-based connectivity, asopposed to the simpler availability-based network connectivity,information on the capability of the neighbor may be used in attemptingto establish a neighbor association. In a related embodiment, additionalcriteria may be applied, such as application requirements, for example,which can supersede the performance-based criteria in some cases.

As illustrated in FIG. 12B, where a neighbor node is selected as theparent for network access using the LR mode, the parent node will switchfrom the very low duty cycle LR-mode beacon broadcast to amuch-higher-repetition-rate associated-neighbor beacon broadcastrepetition rate. Thus, once a parent node has one or moreassociated-neighbor child nodes using LR-mode connectivity, the parentnode communications mode control module 416 is configured to respond byproviding more frequent connectivity opportunities so that informationcan be relayed to and from the network to service the child or childrennode(s) with reduced latency.

The network access and data transfer latency will be dictated by theinterval of the periodic associated-neighbor LR mode beacontransmission. If neighbor nodes connect to a potential parent node butnone forms an associated-neighbor relationship for network access, thereis no requirement for the potential parent node to switch from therelatively infrequent discovery-mode beacon repetition rate to therelatively more frequent associated-neighbor beacon repetition rate. Asa node's status changes with respect to whether it hasassociated-neighbor LR-mode child nodes, it automatically adapts itsLR-mode associated-neighbor beacon broadcast repetition rateaccordingly. In a related embodiment, the LR-mode beacon repetition rateis further adjusted based on one or more of the following factors: thenumber of children/descendants, how often child nodes establishcommunications in response to the LR-mode beacons, the volume of databeing sent or received via LR mode, or application requirements.

In this example embodiment, even while a child node is associated with agiven LR-mode parent, that child node will continue to monitor andutilize collected and maintained LR-mode neighbor information toestablish connections to other neighbors for the purpose of exploringopportunities for better potential network access connectivity than theavailable connectivity through the associated parent node. The childnode will evaluate the neighbor links and their associated communicationperformance by scheduling connections to neighbors that may potentiallyoffer better network access. This continued assessment of nodeneighbors, even if only available using LR mode, will ensure that meshconnection diversity can be maintained even when a node device is onlyable to connect to the network using the low-data-rate LR mode. If aneighbor is found that offers a better-performing network path, the nodewill switch its parent node selection to the new parent node by forminga LR-mode neighbor association with the new neighbor. If that node didnot previously have associated children nodes in LR mode, it will beginthe more frequent LR-mode beacon broadcasts once the new neighborassociation is established. As in the case of SR mode network access,any change of gateway based on a new selected access connection willresult in an explicit discovery request/response update being sent tothe new serving gateway.

In the present example, each child node, even while connected to thenetwork in LR mode, will also monitor for SR beacon transmissions. Inresponse to these SR-mode beacons, each child node may preferentiallyattempt to establish connectivity to the network in that mode. In oneembodiment the default decision criteria for selecting parents andcommunication mode will continue to be the primarily throughput-basednetwork connectivity metric, with application-based criteria also beingincorporated into the neighbor and communication mode selection decisionprocess.

As illustrated above with reference to FIGS. 1D and 1E, regardless ofits own primary mode of access connectivity to the network (LR or SRmode), a node may itself support child nodes connected in either LR orSR mode. For dual-mode nodes, the mode of its own connectivity into thenetwork (via a parent neighbor or directly to the gateway device) doesnot restrict the mode supported for its children nodes to join thenetwork. Furthermore, a node may simultaneously support both SR-mode andLR-mode children independent of the mode it uses to connect to thenetwork.

In the dynamic adaptive, multi-hop mesh environment facilitated byaspects of the invention, nodes are able to continually assess theneighbor environment independent of the communication modes used bydifferent neighbors. This capability ensures that the self-organizing,self-adapting nature of the network is maintained even where single anddual-mode nodes are part of the same network. Other than the timeperiods for transmitting its associated-neighbor beacons to service itschild nodes, the time for monitoring of a LR-mode parent's beacons(where the node's connectivity is via LR mode, and the very low dutycycle background scanning for potential LR-mode neighbors, a node willspend the rest of its time operating in SR mode when not in an activeservice or data transfer connection. While in that idle receive mode thenode will be available and able to communicate with SR-mode, non-primary(non-parent, non-child) neighbor nodes.

One aspect of the invention embodied in this example is the node'sability to coordinate and time-multiplex its dual-mode operation.Accordingly, each node device appears, as much as possible, continuouslyavailable to either or both SR-mode and associated LR-mode neighborswith minimal network access latency. In practice, embodiments of theinvention can achieve an average latency on the order of sub-second(i.e., no more than 100s of milliseconds) initial connectionestablishment opportunity.

In one type of embodiment, a nested time frame structure is establishedthat allows a node device to adapt its LR mode operating capacityaccording to application requirements that it supports or the networkconnectivity that is available. The frame structure can be variablyoperated at a duty cycle of less than 1×10⁴ up to 100%. In one suchapproach, the LR mode cycle is individually adjustable for each nodedevice and allows each node to control the degree of multiplexingsupported between SR and LR modes according to its neighbor associationsand supported application requirements. The duty cycle and framestructure are both defined by a single control parameter, FP. Thecommunications channel can thus be dynamically adjusted tomonitor/provide beacon synchronization for associated neighbors and tomeet the other communications requirements for control, messaging, orconnection-oriented two-way data communications exchanges.

FIG. 13 is a table illustrating sets of predefined communicationsparameters and values that are defined based on selected channelbandwidth and spreading factor, according to one embodiment of LR mode.The bandwidth and spreading factor may be predefined for the systemaccording to expectations of the deployment environment or according tospecific service applications and the data rates/connectivity rangedesired. In one example embodiment, a node device is pre-configured toknow what the defined bandwidth (BW) and spreading factors are for thesystem as part of its factory firmware configuration. In a relatedembodiment, as part of the self-organizing and self-configuring network,the node devices each applies a search routine to determine thebandwidth and spreading factors that are in use. For example, the devicecan start with a 125 kHz BW assumption and search by applying a givenset of spreading factors and searching the frequency spectrum for validcommunications, e.g., beacons. If signals are not found after dwellingon the available frequencies for given intervals of time, the spreadingfactor is changed and the search repeated across the operating spectrum.If no beacons are found at the 125 kHz BW the process of searching isrepeated at 250 kHz BW and, as needed, at 500 kHz. This search processcan be conducted as part of the device's initial deployment when it isnot yet part of the network and is thus able to devote all of its timeto discovery of the BW and spreading factors defined for the network.The data rates listed in the table of FIG. 13 are a function of thebandwidth and spreading factor selections. The values in the additionallink margin column represent the improvement in reception sensitivityprovided by the LR DSSS communications mode (relative to that of the SRFHSS mode). The values for slot size and burst length relate to theduration and data size, respectively, for various fields available in adefined messaging frame according to one embodiment.

FIGS. 14A-14C illustrate an exemplary frame structure for LR-mode framesaccording to one embodiment. This frame scales uniformly with thechannel bandwidth BW and spreading factor SF used for communications ona given link. The limited, selected set of transmission frame sizesallows upper-layer application and network control messages to betransported with within a frame structure where transmission slots sizesare directly selectable as a function of BW and SF while keepingtransmission overheads low.

As depicted, each frame is composed of two segments: a common controland messaging frame segment, and a TX/RX communications frame segmentwhere frequency hopping may be applied for dedicated connection-orientedexchanges. In one particular type of embodiment, the common control andmessaging frame segment is sent on a predefined control channel, whereasthe frequency hopping TX/RX communications frame segment, as its nameimplies, is transmitted according to a predefined frequency hoppingsequence such that this segment, for consecutive transmission/receptionslots, occurs on different, pseudo-randomly selected frequencies.

Each frame is composed of slots having a defined size, t_(s), accordingto the bandwidth (BW) and spreading factor (SF) as follows:

$\begin{matrix}(1) & \; \\{t_{s} = {5\mspace{14mu} {{ms} \cdot \frac{500\mspace{14mu} {kHz}}{BW} \cdot 2^{({{SF} - 6})}}}} & (1)\end{matrix}$

Each burst sent within a transmission slot is structured with a definedset of fields, which can include a header field HDR, that is comprisedof Message Type (T) and Control (C) sub-field, an optional Length (L)field, and an optional Addressing fields, and a variable length messagepayload. The control sub-field may also specify information on theapplication of data security within the transmitted burst. According toone aspect of the invention, the slots can be combined in pairwisefashion to provide an increased payload that adds multiple slot sizes ofpayload space (i.e., removing the overhead of the HDR fields from theadditional slots) to increase the message data payload.

The common control and messaging frame segment includes one or twobeacon/synchronization (BCN) transmission slots, followed by fourreceive mode slots during which responsive data can be received. This isfollowed by one or two transmission slots in which an acknowledgementsor single-slot data messages can be sent. In the embodiment depicted,the common control message frame has a defined cycle duration that isgiven by:

T _(c) =n·t _(s) where for example, n=8  (2)

The transmission frame period is given by:

T _(f)=2^(FP) ·T _(c).  (3)

The frame parameter FP can be transmitted within the common controlchannel beacon/synchronization (BCN) field. As described above, the FPparameter allows a variable operating duty cycle to be efficientlycommunicated by each node device according to its network connectivityand services supported. Neighboring nodes that receive a frame from agiven node device are thus able to formulaically derive the value ofvarious communication parameters that are being used by the nodedevice's LR communication mode as follows:

$\begin{matrix}{\mspace{79mu} {{{Control}\mspace{14mu} {Channel}\mspace{14mu} {Duty}\mspace{14mu} {Cycle}} = \frac{100\%}{2^{FP}}}} & (4) \\{\mspace{79mu} {{{Device}\mspace{14mu} {Control}\mspace{14mu} {Channel}\mspace{14mu} {TX}\mspace{14mu} {Duty}\mspace{14mu} {Cycle}} = \frac{100\%}{2^{{FP} + 1}}}} & (5) \\{{{{TX}/{RX}}\mspace{14mu} {Communication}\mspace{14mu} {Channel}\mspace{14mu} {Capacity}\mspace{14mu} {Allocation}} = \frac{100{\% \cdot 2^{{FP} - 1}}}{2^{FP}}} & (6)\end{matrix}$

With the single control variable, FP, a node device can define itsLR-mode operating duty cycle from less than 1×10⁻⁴ to 100%.

FIG. 14C illustrates the frequency hopping TX/RX communications framesegment in greater detail. This segment has alternating receive andtransmission slots, each having a slot size of 2t_(s). Optionally, asshown, consecutive slots can be combined to increase the payload size,with a total combined slot size of 4t_(s). The alternating receive andtransmission arrangement supports connection-oriented two-way datatransfers.

In a related embodiment, node devices employ a distributed frequencychannel selection scheme where each node autonomously and randomlyselects its LR-mode control channel frequency, rather than using a fixedpredefined control channel frequency. According to this embodiment, thechannel selection and beacon transmission operation is defined tooverlay and operate within the frequency channelization scheme that isdefined for the SR-mode communications. This approach allows the LR-modeoperation to also include frequency hopping for dedicated connections tominimize the interference impact on both SR mode and other LR-modecommunications in the shared communications spectrum's neighborhood.

The embodiments above are intended to be illustrative and not limiting.Other variations are contemplated to fall within the claims. Inaddition, although aspects of the present invention have been describedwith reference to particular embodiments, those skilled in the art willrecognize that changes can be made in form and detail without departingfrom the scope of the invention, as defined by the claims.

Persons of ordinary skill in the relevant arts will recognize that theinvention may comprise fewer features than illustrated in any individualembodiment described above. The embodiments described herein are notmeant to be an exhaustive presentation of the ways in which the variousfeatures of the invention may be combined. Accordingly, the embodimentsare not mutually exclusive combinations of features; rather, theinvention may comprise a combination of different individual featuresselected from different individual embodiments, as will be understood bypersons of ordinary skill in the art.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims that are included in the documentsare incorporated by reference into the claims of the presentApplication. The claims of any of the documents are, however,incorporated as part of the disclosure herein, unless specificallyexcluded. Any incorporation by reference of documents above is yetfurther limited such that any definitions provided in the documents arenot incorporated by reference herein unless expressly included herein.

For purposes of interpreting the claims for the present invention, it isexpressly intended that the provisions of Section 112, sixth paragraphof 35 U.S.C. are not to be invoked unless the specific terms “means for”or “step for” are recited in a claim.

1. A node device for use with a self-organizing wireless multihop network containing a plurality of other node devices and at least one gateway device, each node device being within wireless communication range of one or more neighboring node devices located in a corresponding local neighborhood, the node device comprising: radio communications circuitry configured to both communicate to an upstream node via short-range (SR) communication mode or a long-range (LR) communication mode, and to communicate to a downstream node in either the SR communication mode or the LR communication mode; a controller including a processor and a non-transitory data storage medium containing instructions executable on the processor, wherein the controller is interfaced with the radio communication circuitry; a communication mode control module configured to cause the radio communications circuitry to selectively operate in the SR communication mode or the LR communication mode based upon the instructions from the controller, wherein the SR communication mode utilizes a higher data rate than the LR communication mode for any given communication bandwidth; the communication mode control module controlling operation of the radio communications circuitry to: (a) advertise connectivity link availability for neighboring node devices in both the SR communication mode and the LR communication mode according to a periodicity that is dynamically-variable in response to prevailing circumstances, wherein the prevailing circumstances to which the dynamically-variable scheduling is responsive include a determination of whether any neighboring node device has established a neighbor-associated connection to the node device in a corresponding communication mode, wherein in response to an absence of connections with neighboring node devices in the LR communication mode, the dynamically-variable scheduling of connectivity advertising in the LR communication mode is set to a predefined minimum advertisement repetition rate. and (b) selectively initiate a link in response to connectivity availability advertised by at least one neighboring node device; and the communication mode control module controlling operation of (b) to be selectively performed in one of either the SR communication mode or the LR communication mode, based on selection criteria that include data throughput performance associated with different neighboring node devices with which connectivity is available via a corresponding one of either or both of the SR communication mode and the LR communication mode. 2-13. (canceled)
 14. The node device of claim 1, wherein in response to addition of neighboring node devices connecting to the node device in the LR communication mode, the dynamically-variable scheduling of connectivity advertising in the LR communication mode adjusted to increase an advertisement repetition rate. 15-16. (canceled)
 17. The node device of claim 1, wherein the communication mode control module includes: a new discovery beacon module configured to control the radio communications circuitry to send LR communication mode connectivity link availability beacons at a first repetition rate; and a associated-neighbor module configured to control the radio communications circuitry to send LR communication mode connectivity link availability beacons at a second repetition rate that exceeds the first repetition rate; and a scheduling module that dynamically varies at least the second repetition rate based on the prevailing circumstances, wherein the prevailing circumstances include a quantity of neighboring node devices responsive to the LR communication mode connectivity link availability beacons.
 18. The node device of claim 17, wherein the communication mode control module is configured to cause the radio communications circuitry to: send the LR communication mode connectivity link beacons at the first repetition rate on a dedicated control channel frequency defined from among a set of possible control channel frequencies; and send the LR communication mode connectivity link beacons at the second repetition rate on the dedicated control channel frequency while conducting communications on a plurality of other channel frequencies according to a defined frequency hopping sequence for an communications connection with an established neighbor node device.
 19. In a self-organizing wireless multihop network containing a plurality of node devices and at least one gateway device, each node device being within wireless communication range of one or more neighboring node devices located in a corresponding local neighborhood, a method for operating a node device, the method comprising: (a) performing communications in a short-range (SR) communication mode, and in a long-range (LR) communication mode, wherein the SR communication mode utilizes a higher data rate than the LR communication mode for any given communication bandwidth; (b) advertising connectivity link availability for neighboring node devices based upon prevailing circumstances to which dynamically-variably scheduling is responsive, including a determination of whether any neighboring node device has established a neighbor-associated connection to the node device in a corresponding communication mode, wherein in response to an absence of connections with neighboring node devices in the LR communication mode, the dynamically-variable scheduling of connectivity advertising in the LR communication mode is set to a predefined minimum advertisement repetition rate; and (c) selectively initiating a link in response to connectivity availability advertised by at least one neighboring node device; wherein (b) is performed in both, the SR communication mode, and the LR communication mode, according to a periodicity that is dynamically-variable in response to prevailing circumstances in the local neighborhood; and wherein (c) is selectively performed in one of either the SR communication mode or the LR communication mode, based on selection criteria that include data throughput performance associated with different neighboring node devices with which connectivity is available via a corresponding one of either or both of the SR communication mode and the LR communication mode. 20-31. (canceled)
 32. The method of claim 19, wherein in response to addition of neighboring node devices connecting to the node device in the LR communication mode, the dynamically-variable scheduling of connectivity advertising in the LR communication mode is adjusted to increase an advertisement repetition rate. 33-34. (canceled)
 35. The method of claim 19, further comprising: sending the LR communication mode connectivity link availability beacons at a first repetition rate; and sending the LR communication mode connectivity link availability beacons at a second repetition rate that exceeds the first repetition rate; and dynamically varying at least the second repetition rate based on the prevailing circumstances, wherein the prevailing circumstances include a quantity of neighboring node devices responsive to the LR communication mode connectivity link availability beacons.
 36. The method of claim 35, further comprising: sending the LR communication mode connectivity link beacons at the first repetition rate on a dedicated control channel frequency defined from among a set of possible control channel frequencies; and sending the LR communication mode connectivity link beacons at the second repetition rate on the dedicated control channel frequency while conducting communications on a plurality of other channel frequencies according to a defined frequency hopping sequence for an communications connection with an established neighbor node device.
 37. (canceled) 